1. Technical Field
The disclosure relates to an ultrasound observation apparatus for observing tissue of a specimen using ultrasound waves, a method for operating the ultrasound observation apparatus, and a computer-readable recording medium.
2. Related Art
In ultrasound observation techniques, there is known THI (tissue harmonic imaging) that performs image generation using the nonlinearity of body tissue (see, for example, JP 2013-56033 A). THI is a technique in which a plurality of ultrasound signals having different phases or amplitudes are sequentially transmitted, and received signals that represent ultrasound echoes of the ultrasound signals are subjected to addition, subtraction, or the like, by which a signal whose harmonic component is enhanced is obtained, and based on the signal an image is generated. According to THI, an ultrasound image with improved resolution and reduced artifacts can be obtained.
On the other hand, there is also known a technique in which a feature image that represents differences in tissue characteristics of body tissue is generated using frequency feature of ultrasound scattered in body tissue (see, for example, JP 5114609 B2). In this technique, a frequency spectrum is computed by performing frequency analysis by performing fast Fourier transform (FFT) on a received signal representing an ultrasound echo, and a feature image is generated based on feature which is extracted by, for example, performing an approximation process on the frequency spectrum.